1. The Field of the Invention
The present invention relates generally to audio systems implemented in computer systems and, more particularly, to an audio sound system having interchangeable speakers for use in a computer system. More particularly still, the present invention relates to an audio sound system where the computer system can distinguish between the type of speakers connected to the computer system and optimize the system according to the speakers then connected.
2. Prior Art
Computer systems have expanded to perform many functions and operations. One such function is to provide output and input for various media sources such as audio and video. In the audio portion of computer systems, sound cards have been gaining favor in computer systems. These sound cards, unfortunately, typically do not have adequate power to drive the speakers attached to the computer system.
The speakers that are attached to the computer system and receive the output signal from the sound card typically require internal amplification or self-amplification for driving the speakers. The sound signal comes from the sound card, but the power to drive the speakers themselves is provided by a second source other than the computer. As multimedia functions became better integrated in computer systems, there arose a need to provide direct sound amplification and equalization within the computer system to the speakers themselves. As these speakers became self-driven from the computer system, one problem of providing speakers with amplification and equalization has been overcome.
Once computer designers and builders integrated the amplifier into the computer system, additional integration was then desired. This integration was to optimize the speakers by using sound equalization to match the sound characteristics of the amplifier as well as match the amplifier to the sound characteristics of the speaker in order to improve the sound quality. This optimization required that the speakers be tailor designed towards the system itself and that the amplifier internal to the computer system also be tailored such that the equalization, sound separation, and signal boost and gain would be designed for the particular speakers integrated into the system as a whole. Unfortunately, this integration has led to yet another problem.
The integration of the speakers with the computer system is very much desirable; however, it has introduced the problem of the user lacking the flexibility of customizing the speakers to the user""s own particular taste and pocketbook. For example, various add-on stereo speaker systems can provide much greater frequency response and sensitivity than some systems that are integrated into a computer system. When a user desires to swap out the original speakers for this new speaker system, typically these new multimedia speaker systems are self-amplified. Even when the speaker systems being self-amplified, the amplifier system built into the computer system attempts to drive these speakers, and there is a problem of having too much gain due to cascading of two power amplifiers, which causes severe audio distortion. This can be overcome simply by reducing the amplifier gain. Unfortunately, the stereo sound acoustics and optimization that is done within the amplifier is still passed on to the speakers in such a manner that the speakers, which have been optimized regardless of the system to which they are attached, are now corrupted in that extraneous signals and processing is being forced into the speakers and then the sound quality is degraded and the user is unhappy with the computer system or the new speakers or both.
Accordingly, what is needed is a solution to integrate computer systems with their own speaker system while offering the flexibility of swapping out the integrated speakers with custom-designed speakers selected by the user. The speakers can be either amplified or non-amplified in operation.
According to the present invention, a computer system having automatic speaker detection circuitry is disclosed. The typical computer system includes a central processing unit, a data input device, and a sound card. Further, there is an audio amplifier, as well as an automatic detection and selection circuit that may be within the sound card or the audio amplifier or just part of the computer system as a whole. This automatic detection selection device is able to determine an impedance load of an output device attached to the computer system, namely, a speaker system, and is able to disable the audio amplifier within the computer system upon determining the impedance load and matching that impedance load against a selected value indicating that no amplification of the signal is required for the output device.
Further, an audio sound equalizer is part of the system and can be bypassed in the same manner that the audio amplifier is, namely, that particular impedance load is measured indicating that no equalization is necessary. Additionally, a switching circuit is provided between a first input connector and the speaker load which is, the switching circuit is used to bypass the audio equalizer as well.
The significance of being able to detect from one speaker type to another speaker type is that some speakers are actively driven while other speakers are passively driven. When a speaker is actively driven, it means that it is self-contained with its own power supply and does not need signal amplification from the audio source. On the other hand, passively driven speakers require external amplification, typically from the external signal source. Since actively driven speakers do not need external driving sources, the amplification system in the computer system should be bypassed for optimal performance of the speakers. Likewise, speakers that are matched to the computer system that are passively driven, need the amplification within the stereo system and thus should not be bypassed. This automatic detection occurs when the speakers are connected to the system and the system is turned on and performs its initial power-on self-test and then invokes the BIOS calls for configuring the system with the appropriate components.
The speaker detection apparatus can be embodied in a speaker impedance load detection circuit. This impedance load determination circuit includes a first an input signal connector, a switch, a signal amplifier, an output signal connector, and detection circuitry. The input signal connector is coupled to the switch, as is the signal amplifier and output signal connector. The detection circuitry is coupled between the input signal connector, the signal amplifier, and the output signal connector and is used to detect the impedance value of the connected load so that it can select between a first and second input signal received on the input signal connector via the switch. What the circuit does is it takes the input signal, it passes it to a first channel unamplified or rather through a unity amplification and passes a second channel through an amplifier unit so that an appropriate amplification level can be obtained. Based upon the particular impedance load of the speakers detected, then either the unified or the unity amplified signal is passed to the speaker load, meaning that no amplification is necessary, or the amplified signal is passed to the speaker load, meaning that the speakers are passively driven.
The speaker impedance load determination circuit is such that the detection circuitry includes a capacitor coupled between the signal amplifier and output signal connector and a first switch coupled to the capacitor and the signal amplifier. This capacitor and first switch is arranged so that the capacitor is charged at such a time as to allow the first switch to activate and allow a voltage placed across the output signal connector to a speaker load and the switch in a manner so as to measure the voltage. Once this voltage is determined, then it is a standard calculation to determine the impedance value of the speaker load. Again, this switch is provided to either cut out the signal amplification or also to cut out any audio sound equalization that may be added as well. This speaker arrangement typically is a pair of speakers having a left channel and a right channel and are either self-powered or passively driven.
In order to carry out this particular selection technique, a method is provided for automatically selecting between a first speaker type and a second speaker type. This includes the system first determining an impedance level of the attached speaker load, then selecting the speaker amplification suitable for the attached speaker load based upon this determined impedance level. Additionally, the method can either provide signal equalization, which is based upon the impedance level determined during the initial steps. Further, the system determines the voltage level across the speaker load for calculating the impedance value based on this voltage level. Again, this particular method is performed during the initial power-on self-test within a BIOS call of determining which components are inherent in the system or attached so that proper configuration can be made.